This invention relates to implantable cardiac devices, such as cardiac stimulating devices and cardiac monitoring devices, particularly to those having analog-to-digital converters of the delta modulator type for monitoring intracardial signals.
Implantable cardiac devices, such as implantable cardiac stimulating devices, are used by individuals who have an irregular heartbeat or are at risk of ventricular fibrillation. For instance, pacemakers can stabilize heart function by electrically stimulating the heart at regular intervals. Defibrillators provide a defibrillating pulse to the heart if necessary. In order to provide access to all modes of pacemaker operation, the heart signal must be accurately measured. This allows proper synchronization between the intrinsic heartbeat and the applied electrical pulses of a pacemaker. Intracardial signal monitoring may also be performed to determine whether defibrillation by the cardiac stimulating device is required.
The intracardial signal generally must be digitized so that a digital processor can be used to implement suitable control algorithms. One type of analog-to-digital converter that is suitable for use in an implantable cardiac device is a delta modulator. When a cardiac device is surgically implanted, an analog-to-digital converter must operate with limited battery power reserves. Indeed, the cardiac device is intended to last a lifetime and replacement entails additional surgery, so minimizing overall power consumption in the device is important. This can be achieved in part by lowering the power use of the analog-to-digital converter.
It would therefore be desirable to be able to provide an implantable cardiac device that has lower power consumption than previously known devices.
It would further be desirable to be able to provide a cardiac device that has a low-power analog-to-digital converter for monitoring intracardial signals.
It would also be desirable to be able to provide a low-power delta modulator for use in a cardiac device for monitoring intracardial signals.